| 摘要 |
PROBLEM TO BE SOLVED: To enhance a modulation efficiency of an encoder. SOLUTION: When an incidence light enters an index scale 20 in an inclination, an optical path length of a beam of light A is longer than the optical path length of a beam of light B. A phase difference occurs in both beams of diffraction light that enter a light receiving element 26 due to an occurrence of the difference in the optical path length. Owing to this phase difference, an intensity of a photo-electric detection signal output from the light receiving element 26 varies. That is, the phase difference of the light A and the light B is modulated, due to a periodic fluctuation of an incidence angle of the incidence light, and its interference signal is to be modulated greatly. COPYRIGHT: (C)2008,JPO&INPIT
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